Refining petroleum oils



' April 7, 1942.

REFINING PETROLEUM OIL Filed Sept. 14, 1939 $T7'1 //v6 .SETTL/NG H. C. PAULSEN DocTon $91.0 T'ION DOCTOR SOLUTION J TcRA CE Patented Apr. 7, 1942 2,278,665 REFINING PETROLEUM OILS Henry C. Paulsen, Eliz Standard Oil Develo ration of Delaware abeth, N. J., assignor to pment Company, a corpo- Application September 14, 1939, Serial No. 294,800

Claims.

This invention relates to the refining of petroleum oils. The invention is particularly concerned with refining a gasoline and like products, and especially relates to a process and apparatus for treating sulfur-containing oils with sodium plumbite or analogous lead compounds for the purpose of removing sulfur compounds of the character which render the petroleum oil sour. directed to an improvement in the so -called doctor sweetening operation by which higher quality petroleum products are secured and in which material economies in the process are effected. In accordance with the present invention, the lead mercaptides are converted to disulfides and lead oxide by utilizing hydrogen peroxide in a novel procedure which materially improves the operation. 3 Mineral oil distillates, as for example, petroleum oil distillates boiling in the kerosene and motor fuel boiling range, contain certain sulfur compounds which impart disagreeable odors to the oil. Various methods have been employed.

for the removal of these compounds or-for the conversion of these disagreeable sulfur compounds to innocuous materials. However, these compounds are usually removed by agitating the oils with an alkaline solution of an alkali metal plumbite such as sodium plumbite which is prepared by dissolving lead oxide in an excess of sodium hydroxide. When the petroleum oil and plumbite solution are mixed, a chemical reaction occurs resulting in the conversion of mercaptans to corresponding lead mercaptides. These mercaptides are then decomposed, usually by the addition of free sulfur, resulting in the lead being precipitated as an insoluble lead sulfide and in the formation of odorless disulfide compounds. This operation known as sweetening may be summarized by the following reactions:

This operation is not entirely satisfactory since in order to insure complete removal of the soluble lead compounds from the oil, it is necessary The invention is more particularly h 7 characteristics as well to add a sufiicient amount of sulfur, which oft-f.

times results in the use of sulfur.

line is very' undesirable since it impairs the quality of the gasoline with respect to corrosiveness and anti-knocking properties as measured an excess of elementary. The excess sulfur dissolved in the gaso-.

.quantitative amount of oxide and lead sulfide prove its anti-knocking characteristics, and to improve its susceptibility for knock-suppressing agents, as for example, tetraethyl lead.

Various suggestions have been made for overads are more or less cumbersome and'not entirely satisfactory from a commercial standpoint,- For example, variaus electrolytic methods have been tried in order to accurately determine the amount of sulfur necessary to just quantitatively precipitate the lead. These methods are not entirely practical since the reaction when using the sulfur is very slow in reaching completion which decreases through-puts and equipment capacities.

. I have now discovered a process by which sour oils may be readily treated in the usual manner with an alkaline solution of sodium plumbite or doctor solution and the resulting soluble lead mercaptides completely converted in an eiiicient manner. In accordance with my invention,-these soluble lead mercaptides are converted to lead by theaddition of hydrogen peroxide to the oil containing litharge, thus insuring that the sulfur content of the oil will not be increased and that no undesirable sulfur polymers will be formed. The process of I my invention maybe demonstrated by the following reactions:

My invention necessarily results in the production of a higher quality oil completely free of corrosive sulfur and having high anti-knocking as having a high susceptibility for knock suppressing agents. Possible rerunning of the treated oil for the r moval of undesirable sulfur polymers is eliminated. Furthermore, my process eliminates the regeneration of doctor solution stage since the lead from the hydrogen peroxide treated oil containing litharge is removed as lead mono-oxide by wash- 7 and used as freshing with sodium hydroxide doctor solution.

The process of my invention may be readily understood by reference to theattached drawing illustrating one modification of the same. purposes of description, the feed oil is taken to be a mercaptan containing petroleum naphthav boiling in the motor fuel boiling range.

A solution of sodium plumbite is introduced'into the sweetening system by means of line 4 and is mixed with the sour gasoline in contacting pump 2. The mixture in an initial stage passes through valve 3, mixer 3| and line 5 the- 2. into settling drum 6, wherein separation of the spent doctor solution from the leaded gasoline containing lead mercaptid-es occurs. In the initial stage the mercaptan compounds contained in the oil are converted to oil-soluble lead mercaptides and the spent doctor solution layer segregated from the leaded oil. The leaded gaso line containing lead mercaptides is withdrawn from settling drum 6 by means of line land in a secondary stage mixed with nydrogenper oxide which is introduced by means of line 12 and contacting pump l9, the mixture withdrawn from contacting pump ID, by means, of line H and introduced into settling drum l3, wherein separation of the spent aqueous hydro gen peroxide solution from the gasoline contain ing suspended lead oxide occurs. In the secondary stage, the lead mercaptides are reacted with hydrogen peroxide under conditions to forrn an oil layer containing lead oxide and a spent aqueous solution of hydrogen peroxide, The spent aqueous peroxide solution is withdrawn from settling drum l3 by means of a level control valve 15 and line IS; The oilcontaining suspended lead oxide is withdrawn from settling drum l3-by means of line It, and in a tertiary stage contacted with spent doctor solution from said initial stage under conditions whereby a treated substantially lead-free oil phase containing disulfides and a regenerated doctorsolu; tion phase are formed. The oil withdrawn by means of line i4 is passedthrough'contacting pump I! wherein it is mixed with "spent doctor solution withdrawn from settler 6 by means of line 9. This mixture is withdrawn from 'c'on tacting pump H by means of line lBiand intro duced into settling drum' l9. The'regenerated doctor. solution separates from the sweetened gasoline in settling drum N and iswithdrawn from settling drum I5 through valve'2i and then passed into doctor solution storage ZSby means of line 22. The doctor solution is withdrawn mm doctor solution storage 29 by means of line 4 and: mixed with freshunsweetened "gasoline in com, tacting pump 2. Fresh doctor solution m ay be introduced in the system by means of line 32. The sweetened gasoline substantially free of lead oxide is Withdrawn from settling drum. 18, by means of line 28 and passed into mixing'column 24 along with water which is introduced by means of line 23. The water-gasoline mixture is withdrawn from mixing column by means of 3 line 25 and passed into settling'drum .25 lawma the added water is separated from the sweetened. washed gasoline. The water iswithdrawn. from settling drum 26' by meansofa liquid level con trol valve 21 and line 28, while the finishedsweet ened gasoline is withdrawn from settling' 26 by means of line 30 and passed, to'finished gasoline storage.

Liquid level control'valves. 8, e

peroxide concentration of from 5 to 10%. When using aqueous solutions of peroxides of these concentrations, it is suflicient to contact the lead mercaptidecontaining oil with from about 2 to 10 of aqueous. peroxide solution.

The process of the present invention is not to be limited by any theory or mode of operation, butonlyin and by the following claims in which it is desired to claim all novelty in so far as the 12 71 a e mi Lclairn;

1..Process for. converting mercaptan compounds contained in the petroleum oil to disulfide compounds, comprising contacting said petroleum oil in an initial stage with a sodium plumbite solution under conditions ,to convertthe mercaptan compounds to corresponding soluble lead mercaptides, separating the spentsodium plumbite solution from the treated oil containing th soluble lead mercaptides, passing the treated oil fraction into a secondary stage and contacting the same in said selcondary stage withhydrogen peroxide under conditions to convert the lead mercaptides to lead oxide and disulfide com pounds, whereby a water layer is formedin said secondary stage, separating thewater froin the treated oil, passing the treated oil containing sol; uble lead disulfides and the lead oxide to a tertiary stage and contacting the treated oil in said tertiary" stage with the spent alkali metal plumbite solution removed from said initial stage whereby the lead oxide is completely removed from said treated oil.

2. Process as defined by claiml; in whio h said alkali metal plumbite solution is a sodium plumbitesolution.

3. Process as defined by claim 1, in wnicnthe spent alkali metal plumbite solution containing the lead oxide is removed from "said tertiary stage, and recycled to said initialstage.

4. Continuous process for convertingmerc aptan compounds contained in a petroleum oil to disulfide compounds which comprises passing saidoil continuously through an initial, a e condary, and a tertiary-stage, contaoting'said oil insaid initial stage with a sodium plumbite solu; tionunder conditions to convert the mercapta n compounds to corresponding lead mercaptides,

separating the spent alkali metal plumbiteso lu tion and the treated'oil and withdrawing the said Y i spent alkali metal plumbite solution and the said l5, 2| and 21 control thelevel of'the'heavier.

layers which are withdrawn from the :bottom of. the respective settlers. It is to be understood. that any desirable mixing, heating, cooling, or distributing means may be employed. The process of the present. invention. may widely vary. Although elevated temperatures and pressures may be employed, it is preferred. to: contact the gasoline with the doctor solution at ordinary temperatures amount of hydrogen peroxide introduced should. be sufiicient to completely convert all solubledead. compounds to lead oxides. Ingeneral. it fis preferred to use aqueous peroxide solutions of 1-to 20% peroxide concentration, preferablyfhavinga and pressures. The.

- alkali metal plumbite solution layer containing thelead oxide are formed, separating the layers and.withdrawing.the said treated oil layer and the saidspent alkali metal plumbite solution froml oil from said initial stage, contacting the, treated oil removed from said initial stage in saidsec ondary stage with hydrogen peroxide under conditions to convert the lead mercaptides to lead oxide and disulfide compounds, whereby a water layer is formed, separatingthe water-layerl from the treated .oil con'taining lead oxideand withdrawing the said water layer and the said. treated oil containing lead oxide ,from said secondary stage, contacting the tr e atedioil withdrawn.f1'omsaid secondary stage in'lsaid tertiary stage with the spent alkalt metaliplumbite solution with-l drawn fromthe initial stage, wherebyatreated oil layer completely free of oxide and a spent said tertiary zone 5.; Process as defined by claim 4. in which the. spentxalkali metal plumbite solution containing, the lead oxide is removed-from saidttertiary.

stage and recycled. to said initial stage.

HENRY- C. 

